/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     licenses@blazegraph.com

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 * Created on Mar 1, 2012
 */

package com.bigdata.rdf.sparql.ast.service;

import com.bigdata.bop.IBindingSet;
import com.bigdata.rdf.sparql.ast.eval.AbstractServiceFactoryBase;
import com.bigdata.striterator.ClosableEmptyIterator;

import cutthecrap.utils.striterators.ICloseableIterator;

/**
 * This service factory will always produce empty result.
 * For use for SILENT SERVICE, etc.
 */
public class NullServiceFactory extends AbstractServiceFactoryBase {

    /**
     * Options configuring this service as a native Blazegraph service.
     */
    private static final BigdataNativeServiceOptions SERVICE_OPTIONS = new BigdataNativeServiceOptions();

    @Override
    public BigdataServiceCall create(final ServiceCallCreateParams params) {

        return new NullServiceCall();

    }

    @Override
    public IServiceOptions getServiceOptions() {
        return SERVICE_OPTIONS;
    }

    private static class NullServiceCall implements BigdataServiceCall {

        @Override
        public IServiceOptions getServiceOptions() {
            return SERVICE_OPTIONS;
        }

        @Override
        public ICloseableIterator<IBindingSet> call(IBindingSet[] bindingSets)
                throws Exception {
            return new ClosableEmptyIterator<IBindingSet>();
        }

    }

}
